This invention relates to pieces of jewelry such as for instance watchcases, watchbands, bracelets, rings, cuff links, brooches, pendants and the like, which are protected by a sintered hard metal shielding, and more particularly to the means for anchoring thin shielding plates of sintered hard metal to a body member made out of a material suitable for machining.
With the pieces of jewelry of this type, which are known in the art, securing the protecting pieces to the body member of the piece of jewelry is achieved by welding as shown in U.S. Pat. No. 3,242,664.
This securing method is, however, not easy. By welding a sintered hard metal thin plate to a steel body member, for instance, the hard metal plate undergoes strong stresses, due to the different coefficients of thermal expansion of the materials involved. Moreover, at the welding temperatures, ranging about 1000.degree. C., it is not possible to give the protecting piece its final appearance before welding. That piece has thus to be finished after welding. It should, however, be noted that these finishing operations, which include polishing, are the most arduous and also the most delicate, so that they cause the most numerous waste, thereby involving not only the loss of the hard metal piece, but also that of the whole body member already secured thereto. The long sequence of manufacturing operations with that known method has also great delays in delivery as a consequence. Finally, if polishing has to be followed by coloring the hard metal piece, the parts of the piece of jewelry, which shall not be colored, have to be masked and then, after coloring, to be uncovered again thus complicating the finishing operations even more while slackening their progress and increasing the risk of waste.
In practice, one resorted to bulky protecting pieces rather than to thin plates for shielding the pieces of jewelry. Moreover, in order to enable entire finishing of body members of material suitable for machining and the sintered hard metal protecting pieces every one for itself, gluing these two pieces to one another has been contemplated.
Unfortunately, gluing is not absolutely reliable. Under certain climates, glues undergo a breakup.
For ensuring the required anchoring, mechanical fixing means have also been proposed, even those comprising "latches" made out of rubber-like material as shown in U.S. Pat. No. 3,643,423.
However, that method of securing the two pieces in question to each other requires precise shapes and sizes of both the body member made out of a material suitable for machining and the sintered hard metal protecting piece, thus rendering the manufacture, in particular of the protecting piece, cumbersome, because of the relatively important shrinkage which the latter undergoes during sintering and because it must be given an appropriate shape before sintering, if one wishes, thereafter, to avoid expensive machining operations.
Long before using sintered hard metal with pieces of jewelry, those skilled in the art have had the idea of making a body member out of a material which can easily be machined and of protecting that body member by means of a shielding made out of a harder material as shown in Swiss Pat. Nos. 181,293 and 236,616. However, that known shielding consisted in a sheet of a material which was still malleable, such as stainless steel, and which can, accordingly, be shaped at will without difficulty, either by folding or swaging, in order to cover the softer body member of the piece to be protected and to be secured thereto merely by wrapping the body member or in any other mechanical manner, for instance by crimping, pinching and the like.
The means which were used for securing such a shielding to the body member which was to be protected can, however, not be utilized with a sintered hard metal shielding.
For securing a thin plate onto the body member of a piece of jewelery, mechanical anchoring means operating without an intermediate latch are also known in the art as shown in French Pat. No. 2,264,501.
In order safely to retain the dovetailed tenon in the corresponding slide, those known anchoring means, however, require an elastic deformation of the plate, which cannot be expected from a sintered hard metal plate.